1. Field of the Invention
The present invention relates to bolts and threaded studs. More particularly, the present invention relates to novel bolts and threaded studs having indicating means for indicating when the bolt or stud is fully engaged in a blind hole.
2. General Background of the Invention
High-pressure vessels use bolts to hold down covers. When studs or bolts are not fully engaged in their bolt holes, the structural integrity of high pressure dome tank cars is compromised. These bolts are usually screwed into "blind" holes (that is, holes which do not protrude through the wall of the vessel, but instead are closed at the bottom). Due to the high pressure of the contents of the vessels, it is desirable to have as many threads of the bolt as possible engaging the threads of the hole. Therefore, it is desirable to use as long a bolt as possible for a given hole. However, it is not easy to determine whether the bolt in a given hole is as long as possible.
The present invention was conceived to solve the problem of field inspection of high-pressure domes on railway tank cars. Currently, inspection of bolts and studs on these tank cars is done electronically using expensive equipment and skilled personnel.